Vapor generator furnace



May 29, 1956 A. sl'FRlN 2,747,553

VAPOR GENERATOR FURNACE Filed Aug. 25, 1951 ATTORNEY United States VAPOR GENERATR FURNACE Andreas Sifrin, berhausen, Germany, assigor to The Babcock & Wilcox Company, Rockleigh, N. J., a corporation of New Jersey TheV present invention relates to furnaces and more particularly to the construction and operation of a multichambered furnace structure especially adapted for the combustion of ash-containing solid fuels and for the utilization of heat derived from the resulting gases of combustion.

More specifically the invention relates to an improved construction of a vapor generator furnace structure having a plurality of fuel burning compartments or primary chambers from which the heating gases are discharged into a common secondary chamber prior to passage into contact with fluid heating elements. in the particular embodimentv disclosed, the separate fuel burning chambers are provided by cyclone furnaces of the general type disclosed in U. S. Patent Bailey et al. 2,357,301, September 5, 19'44. During operation of the cyclone furnaces, the residual ash is maintained molten so as to drain into the common chamber from which it is similarly discharged as liquid slag for ultimate disposal. Furthermore, the common chamber is provided with suitable slag catching means whereby gas entrained slag particles are separated from the gases and combined with other collected slag at the bottom of the chamber.

Heretofore, when two or more cyclone furnaces have been employed to discharge into a common chamber, it has been customary to arrange the furnaces in spaced relation along a single wall of the secondary chamber, with the central axis of the respective furnaces lying parallel and alongside of each other. With such an arrangement, due to the high velocity at which the gases of combustion are discharged from the individual furnaces, it may not be possible to bring about av condition wherein the gases are completely and uniformly distributed throughout the entire volume of the secondary chamber in order to obtain a thorough mixing of hot gases from the respective furnaces.

An object therefore of the present invention is to provide an improved form of furnace structure whereby the hot gases discharging from a plurality of cyclone furnaces are distributed throughout the entire cross section of the secondary chamber prior to passage into contact with the major heating surface of the unit. In order to produce such a result, the lower part of the secondary chamber is constructed in the form of a well or mulfl'e of symmetrical crossk section about a vertical axis, while the cyclone furnaces are arranged so as to discharge into the well in such a manner as to generate a rotating body of heating. gases about the axis of the well. In the particular form herein disclosed, the well is of equila-teral polygonal crossV section in a horizontal plane and the cyclone furnaces are arranged in separate walls at regular intervals about the vertical axis.

Thevarious features of novelty which characterize my inventionare pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding ofthe invention, its operating advantages and speciiic objects attained by its use, reference should be had to the accompanying drawings andarent 2,747,553 Patented May 29, 1956 descriptive matter in which I have illustrated and' described a preferred embodiment of my invention.

Of the drawings:

Fig. 1 is a side sectional view of a cyclone furnace unit constructed in accordance with the invention, the section being taken along line 1-1 of Fig. 2; and

Fig. 2 is a sectional plan view of the unit taken along line 2-2 of Fig. l.

The illustrative embodiment of the invention comprises a plurality of cyclone furnaces 3, 4, 5 and 6 arranged to discharge into a common secondary chamber 7 from different directions. The lower part of the chamber is of symmetrical cross section about a vertical axis and specifically is enclosed by upright fluid cooled Walls 8 arranged in the form of a square. The primary cyclone furnaces 3, 4, 5 and 6 are of the same general type as disclosed in the aforesaid' U. S. Patent 2,357,301 and thus are essentially horizontally inclined cylinders of water cooled construction. As illustrated herein, each cyclone furnace is mounted in a separate wall 8 at a location adjacent the next succeeding wall, with the central axis of its cylindrical combustion chamber 10 lying in a vertical plane arranged at right angles to the wall in which the cyclone furnace is mounted, and thus in parallel relation to the succeeding wall. In this manner, the cyclone furnaces associated with each pair of opposing walls 8 are assembled with their central axes in parallel vertical planes, as indicated in Fig. 2 and, in the respective planes, are inclined downwardly toward chamber 7 as seen in Fig. l. Moreover, as also indicated'in Pig. 2, the vertical planes containing the central axes of all cyclones S, 4, 5 and 6 are tangent to a central cylindrical furnace region i2.

ln conformity with the disclosure of the aforesaid patent, each cyclone furnace includes a coaxially arranged. fuel inlet section l5 into which a fuel-air mixture is introduced tangentially at high velocity from a primary airfuel conduit 36. A major proportion of the total air required for combustion is introduced into the main chamber lo through a tangentially directed secondary air port 17 which is provided intermediate the ends of the chamber at its maximum diameter. Additional air may be introduced tangentially from an air supply duct i8. In the opposite end wall 19, a reentrant throat section Ztl provides a central gas outlet 21. A slag outlet 22 is formed in the lowermost portion of Wall 19 to permit drainage into secondary chamber 7'. The walls of each cyclone chamber 10 are formed with fluid heating tubes 14 which are suitably arranged and connected in known manner to provide active circulationof cooling fluid therethrough.

Chamber 7 is formed with a conical bottom having inclined refractory portions 23 which converge downward.- ly to a central slag outlet 24. At an elevation above the cyclone furnaces, at least two opposing walls 8, such as the walls in which furnaces 3 and 5 are assembled, are assembled, are extended outwardly and upwardly as at 25, and thereabove are continued vertically as at 26 so as to define an upper radiation Zone or space` 27 of considerably greater width and volume than the lower secondary chamber space 7. The remaining two opposing walls 3, in which furnaces 4 and 6 are assembled, are continued vertically at increasing widths so as to complete the lateral boundaries of the chamber. As will be understood, the enlargement of the upper end of chamber 7, in the manner described, provides the additional amount of space required for suitable accommodation of a large proportion of the heat absorbing elements of the unit.

The walls surrounding the secondary chamber 7 are cooled by means of fluid heating tubes 31 and 32 which, together with the cyclone furnace wall tubes 14, and

other heat absorbing elements, not shown, in and beyond the radiation chamber 27, combine to form the total vapor generator surface receiving heat from furnaces 3,4,5and.6. i

In each of the opposing walls 8, 8 in which cyclones 4 and 6 are mounted, tubes 3l are connected at their lower ends to a lower header 32 and extend upwardly therefrom as indicated in Fig. l, with certain tubes 31a bent in semicircular form, as shown, so as to embrace the respective throat passages 21.

In opposing walls S, S in which cyclones 3 and S are mounted, tubes 34 are connected at their lower ends to lower headers 35 and extend therefrom along oppositely arranged inclined floor portions 23, with certain tubes 34 being disposed in horizontally spaced screen formation across the slag outlet 24. From positions in and along the floor, tubes 34 extend upwardly along opposing walls 8, 8 in which cyclones 3 and 5 are mounted, with certain tubes 34a bent to embrace the gas outlets 21. Above the cyclones, the tubes 34 in opposite walls 8, are divided into groups, with one group of tubes 34h in each wall continuing upwardly along the same wall 8,l and a second remaining group of tubes 34C extending across the furnace in vertically spaced inclined rows and then continuing in a single row along the opposite wall portions 25 and 26 in interspersed relation with tubes 34b. As will be understood, the oppositely inclined tube lengths 34C from opposite walls are arranged in horizontally spaced interspersed relation and thereby combine to form a slag catching grid or screen 36 by which gas entrained slag particles are separated from the gases for removal with molten slag discharging through slag outlet 24.

In the operation of each of the cyclone furnaces 3, 4, and 6, an ash-containing solid fuel such as coal, in crushed or coarsely pulverized condition is supplied to the fuel inlet section in a high velocity stream of primary air so as to impart a whirling motion to the fuel particles which are discharged into the main combnstion chamber 10 where additional air is supplied tangentially through the secondary air port 17. The lighter fuel particles mainly burn in suspension while the heavier fuel and ash particles are thrown outwardly and caught on the slag layer which forms on the circumferential wall areas. A vigorous scrubbing action takes place between the air and entrapped coal particles, and combustion proceeds at a rate sufficiently high to cause furnace chamber temperatures to be maintained above the ash fusion temperature and thereby permit the removal of ash in the form of liquid slag.

In the construction of furnace disclosed, the gases discharging from the respective cyclone furnaces are directed at high velocity into the secondary furnace 7 and specifically into a lower end portion thereof which is formed as a gas receiving mule or well of considerably smaller horizontal cross section than the horizontal cross section of furnace 7 at higher elevations and furthermore of symmetrical horizontal cross section about a central vertical axis. Moreover, the gases entering the lower well portion are directed tangentially of a central space' 12 of cylindrical formation about a Vertical axis so as to produce a rotation of the total gas body about the central axis of the well.

The introduction of gases at different points throughout the perimeter of the secondary furnace 7, and the rotation of gases within the lower end portion of the furnace serves to bring about an intermixing of the total entering gases and thereby provide substantially uniform gas temperature conditions throughout the entire body of gases entering the radiation chamber 27. TheI quadratic form of furnace cross section does not interfere with the rotary gas movement because the corners are filled up by the entering gas streams. However, if fewer than four cyclone furnaces are to be operated continuously, for lower heat output requirements for example, a well chamber 7 of circular cross section would be more favorable. Due to the high angular Velocity of gases within the well, any slag still contained in the gases is for the most part hurled out, and ows down along the walls 8 and along the floor areas 23 to the discharge opening 24. Additional gas-entrained slag, if an, is removed by the slag-catching grid 36. At partial loads, when one or two of the cyclone furnaces are shut down, or are disconnected, a rotation of the gases will still develop.

`While in accordance with the provisions of the statutes I have illustrated and described herein the best form of my invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of my invention may sometimes be used to advantage without a corresponding use of other features.

I claim:

1. ln a vapor generator furnace comprising a primary and a secondary furnace chamber of which the primary chamber is provided by a cyclone type furnace in which the combustion of ash-containing solid fuel is substantially completed at temperatures above the ash-fusion temperature, said cyclone type furnace being of substantially cylindrical formation about a horizontally arranged 1ongitudinal axis, means dening said secondary furnace chamber comprising two upright Walls arranged in opposed relation of which a lower portion vof one wall is formed with separate outlets through which gases and slag are received from said cyclone type furnace said opposing walls diverging upwardly at an elevation superjacent the position of said cyclone type furnace, and fluid heating tubes arranged upright in rows adjacent the inner faces of the respective walls with selected tubes associated with said one wall having portions bent to embrace the respective gas and slag outlets, said tubes associated with the respective opposing walls having upper tube length portions inclined upwardly in interspersed relation across said secondary chamber at an elevation above said gas outlet and forming a slag-catching grid in the path of upwardly flowing gases, said secondary furnace having a horizontally arranged bottom formed with a slag outlet therein, said rows of lluid heating tubes continuing downwardly along said opposing walls and across said bottom and having portions arranged at horizontally spaced positions across said slag outlet.

2. Apparatus for burning a slag forming fuel comprising a plurality of primary fuel burning furnaces each of substantially cylindrical formation about a horizontally arranged axis, said primary furnaces being of a type in which the combustion of ash-containing solid fuel is substantially completed therein at temperatures above the ash-fusion temperature, a secondary chamber having upright wall portions defining a lower slag collecting section of said chamber of symmetrical cross section about a central vertical axis, said upright wall portions being arranged at substantially equal spacings from said vertical axis, said primary furnaces being arranged at substantially equal spaced locations relative to said vertical axis and each having an end wall formed with a gas outlet and a subjacent molten slag outlet opening into said lower slag collecting section, said primary furnaces being arranged with their horizontal axes in separate vertical planes respectively parallel and adjacent to the nearest adjacent upright wall portions of said lower slag collecting section and tangent to a central upright imaginary cylinder of substantial diameter in said lower slag collecting section at locations circumferentially spaced about said vertical axis, whereby slag is deposited by centrifugal action on the upright wall portions of said slag collecting section from the gases rotating therein, and means for discharging molten slag from said slag collecting section.

3. Apparatus for burning a slag forming fuel comprising a plurality of primary fuel burning furnaces each of substantially cylindrical formation about a horizontally arranged axis, said primary furnaces being of a type in which the combustion of ash-containing solid fuel is substantially completed `therein at temperatures above the ash-fusion temperature, a secondary chamber having upright wall portions defining a lower slag collecting section of said chamber of substantially square cross section about a central vertical axis, said upright wall portions being arranged at substantially equal spacings from said vertical aXis, said primary furnaces being arranged at substantially equal spaced locations relative to said vertical axis and each having an end wall formed with a gas outlet and a subjacent molten slag outlet opening through a corresponding upright wall portion into said lower slag collecting section, said primary furnaces being arranged with their horizontal axes in separate vertical planes respectively parallel and adjacent to the nearest adjacent upright wall portions of said lower slag collecting section and tangent to a central upright imaginary cylinder of substantial diameter in said lower slag collecting section at locations circumferentially vspaced about said vertical axis, whereby slag is deposited by centrifugal action on the upright wall portions of said slag collecting section from the gases rotating therein, and means for discharging molten slag through the bottom of said slag collecting section.

4. Apparatus for burning a slag forming fuel comprising a plurality of primary fuel burning furnaces each of substantially cylindrical formation about a horizontally arranged axis, said primary furnaces being of a type in which the combustion of ash-containing solid fuel is substantially completed therein at temperatures above the ash-fusion temperature, a secondary chamber having upright wall portions defining a lower slag collecting section of said chamber of symmetrical cross section about a central vertical axis, said upright wall portions being arranged at substantially equal spacings from said vertical axis, said primary furnaces being arranged at substantially equal spaced locations relative to said vertical aXis and each having an end wall formed with a gas outlet and a subjacent molten slag outlet opening into said lower slag collecting section, said primary furnaces being arranged with 4their horizontal axes in separate vertical planes respectively parallel and adjacent to the nearest adjacent upright wall portions of said lower slag collecting section and tangent to a central upright imaginary cylinder of substantial diameter in said lower slag collecting section at locations circumferentially spaced about said vertical axis, whereby slag is deposited by centrifugal action on the upright wall portions of said slag collecting section from the gases rotating therein, means for discharging molten slag from said slag collecting section, and groups of oppositely arranged wall cooling tubes extending across the upper portion of said slag collecting section and defining slag screens in the path of the gases leaving said slag collecting section.

References Cited in the file of this patent UNITED STATES PATENTS 1,944,330 Lasker Jan. 23, 1934 1,993,072 Murray Mar. 5, 1935 2,243,909 Kruger June 3, 1944 2,357,301 Bailey et al. Sept. 5, 1944 2,357,303 Kerr et al Sept. 5, 1944 2,363,875 Kreisinger Nov. 28, 1944 

2. APPARATUS FOR BURNING A SLAG FORMING FUEL COMPRISING A PLURALITY OF PRIMARY FUEL BURNING FURNACES EACH OF SUBSTANTIALLY CYLINDRICAL FORMATION ABOUT A HORIZONTALLY ARRANGED AXIS, SAID PRIMARY FURNACES BEING OF A TYPE IN WHICH THE COMBUSTION OF ASH-CONTAINING SOLID FUEL IS SUBSTANTIALLY COMPLETED THEREIN AT TEMPERATURES ABOVE THE ASH-FUSION TEMPERATURE, A SECONDARY CHAMBER HAVING UPRIGHT WALL PORTIONS DEFINING A LOWER SLAG COLLECTING SECTION OF SAID CHAMBER OF SYMMETRICAL CROSS SECTION ABOUT A CENTRAL VERTICAL AXIS, SAID UPRIGHT WALL PORTIONS BEING ARRANGED AT SUBSTANTIALLY EQUAL SPACINGS FROM SAID VERTICAL AXIS, SAID PRIMARY FURNACES BEING ARRANGED AT SUBSTANITALLY EQUAL SPACED LOCATIONS RELATIVE TO SAID VERTICAL AXIS AND EACH HAVING AN END WALL FORMED WITH A GAS OUTLET AND A SUBJACENT MOLTEN SLAG OUTLET OPENING INTO SAID LOWER SLAG COLLECTING SECTION, SAID PRIMARY FURNACES BEING ARRANGED WITH THEIR HORIZONTAL AXES IN SEPARATE VERTICAL PLANES RESPECTIVELY PARALLEL AND ADJACENT TO THE NEAREST ADJACENT UPRIGHT WALL PORTIONS OF SAID LOWER SLAG COLLECTING SECTION AT LOCATIONS CIRCUMFERENTIALLY SPACED INARY CYLINDER OF SUBSTANTIAL DIAMETER IN SAID LOWER SLAG COLLECTING SECTION AT LOCATIONS CIRCUMFERENTIALLY SPACED ABOUT SAID VERTICAL AXIS, WHEREBY SLAG IS DEPOSITED BY CENTRIFUGAL ACTION ON THE UPRIGHT WALL PORTIONS OF SAID SLAG COLLECTING SECTION FROM THE GASES ROTATING THEREIN, AND MEANS FOR DISCHARGING MOLTEN SLAG FROM SAID SLAG COLLECTING SECTION. 